The dehydration of alkane- and alkenediols to cyclic ethers is well known in the art. The reaction can be carried out in the presence or absence of a homogeneous or heterogeneous catalyst, usually an acidic catalyst. It is known, for example, that butane- and butenediols can be dehydrated to furan and/or partially and/or completely saturated furans, such as 2,3-dihydrofuran, 2,5-dihydrofuran and tetrahydrofuran. Catalysts known in the art for such dehydrations include organic and inorganic acids, such as sulfuric and hydrochloric acids, Na.sub.2 Cr.sub.2 O.sub.7 /H.sub.2 SO.sub.4, pyridine hydrochloride and salts providing halide ions, water-insoluble metal oxides and salts, for example, oxides of Al, Ti, Zr and Th, neutral phosphates of Al, Fe, Ce, Ag and U, silica gel, bleaching earths and acid-type heterogeneous materials, such as aluminas and alumino-silicates. Typical of the art of such dehydrations of butenediol in Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973, page 184 wherein is disclosed a study of the dehydration of 2-butene-1,4-diol using acid-type catalysts. The major products of the dehydration are disclosed to be 2,5-dihydrofuran, crotonaldehyde and furan.
U.S. Pat. No. 3,812,158 discloses the preparation of 2,5-dihydrofuran from 3,4-epoxy-1-butene, 3,4-dihydroxy-1-butene or 1,4-dihydroxy-2-butene, in yields of about 15 to 35%, using a soluble mercury salt in a neutral or acidic hydroxylic solvent in the liquid phase at 5.degree.-150.degree. C. Soluble mercury salts include mercury (II) sulfate, chloride, acetate, nitrate, chromate and fulminate and mercury (I) chlorate, chromate and acetate. Other useful mercury compounds include those which can be converted to a soluble salt in the solvent or a component of the solvent, for example, mercury (II) oxide which can be converted to the soluble sulfate by means of sulfuric acid.